Agro-Science Journal of Tropical Agriculture, Food, Environment and Extension Volume 7 Number 3 September 2008 pp ISSN

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1 1 Agro-Science Journal of Tropical Agriculture, Food, Environment and Extension Volume 7 Number 3 September 2008 pp ISSN SOIL PROPERTIES AND INTENSIFICATION OF TRADITIONAL FARMING SYSTEMS IN SUB SAHARAN AFRICA (SSA) Asadu 1 C. L.A, Nweke 2 F.I. and Enete 3 A. A. 1 Department of Soil Science, University of Nigeria, Nsukka, Nigeria 2 Department of Agricultural Economics, Michigan State University, East Lansing, USA 3 Department of Agricultural Economics, University of Nigeria, Nsukka, Nigeria ABSTRACT Population and market pressures are generally accompanied by land use intensification practices such as reduced fallow and increased soil fertility maintenance strategies. However, the extent to which these soil maintenance strategies are adequate compared to natural soil fertility regeneration through fallowing needs to be established. This paper compares soil properties between high and low population pressure areas on one hand and between good and poor market access areas on the other, with the aim of examining the effect of intensification on them. The study that generated the primary data was carried out in sub-saharan African countries within the framework of the Collaborative Study of Cassava in Africa (COSCA). The result of the analysis showed that although the use of all the soil maintenance strategies increased with population and market pressure, soils of the high population density and good market access areas were found to be generally poorer than those of the low population density and poor market access areas. This suggests that the intensification practices in the high population density and good market access areas are not adequate enough to counter the effect of short/no fallow. This underscores the need for credit availability to smallholder farmers to enable them apply the required specification of soil maintenance practices. Keywords: Farming-System, Intensification, Soil Properties, Sub -Saharan Africa INTRODUCTION In the past, African farmers have tended to rely almost exclusively on nature restoring mechanisms for the maintenance of soil fertility. That was achieved through shifting cultivation or bush fallow system. The basic feature of shifting cultivation therefore, is the cost free, effortless regeneration of soil productivity during the fallow period especially when the fallow consists of forest or bush vegetation (Ruthenberg 1980). Here, almost all the organic matter produced by the vegetation is returned to the soil and the fallow vegetation draws up nutrients to the topsoil which helps to build up the soil structure (Ruthenberg 1980). This system is generally referred to as the extensive system. The stability of this system is today generally no longer feasible because of factors such as high rate of population growth, more technical innovations, the growth of urbanization and improved marked access. The prevailing situation is that farmers are forced to intensify land use by reducing fallow periods to a level that is below the minimum required for the sustainability of the soil nutrient. Hence there is need for alternative, appropriate and adequate soil maintenance strategies to counter the effect of fallow reduction on soil fertility. The intensive land use, along with its corresponding intensive use of soil maintenance strategies constitute the intensive system. Many earlier findings agree that the change towards a more intensive agriculture accompanied by all the components of modern technology can raise food production up to and even above the level of the natural fallow vegetation (Boserup 1965, Fresco 1986, Ruthenberg 1980, Alia 1984, Nweke et al. 1984). However, despite the presence of some of these intensification factors, particularly population and market pressure and the subsequent shift towards land use intensification in many regions of Africa, per capita food production remains on the decline (FAO 2002). It might be that the soil maintenance strategies of these farmers are not adequate enough to prevent soil degradation which often leads to

2 Soil Properties and Intensification of Traditional Farming Systems in Sub Saharan Africa (SSA) 2 low crop yield. Ruthenberg (1980) argued that intensification of traditional farming systems postpones, but does not avert involution and eventual impoverishment due to population growth. This paper compares soil properties (Avail P, Total N, organic matter, ph (H 2 O), Ca ++, K +, Mg ++, Na +, TEB, TEA, ECEC, BS, EPP, ESP, C:N ratio, Mg:K ratio, Ca:Mg ratio) between high and low population pressure areas on one hand, and between good and poor market access areas on the other hand. Earlier studies on the effect of intensification on soil properties (Lagemann 1977) was restricted to only three villages of one state in southeast Nigeria, and population pressure was the only factor considered. The present study not only presents a wider coverage (four countries of sub Saharan Africa) but also includes market pressure as a factor in land use intensification. The aim was to examine the effect of agricultural intensification on soil properties. The two indices had earlier been listed as factors that drive land use intensification. MATERIALS AND METHODS Site Selection and Sampling Procedures Climate, human population density, and market infrastructure formed the bases for sampling. Following Carter and Jones (1989), four basic climatic zones were defined from temperature and duration of dry periods within the growing seasons (see also Jones 1988) (Table 1). All-weather roads, railways and navigable rivers were derived from the 1987 Michelin travel maps and used to create a market access infrastructure map of sub-saharan Africa. This map was divided into good and poor zones according to the density of the roads, railways or navigable waterways (see also Asadu et al. 2007). Population data from the United States Census Bureau (unpublished data), projected forward to 1990, were used to calculate population densities and to create a population map of Africa. This map was divided into high and low demographic pressure zones, the former comprising areas with 50 or more persons per km 2 (see also Nweke et al. 1994) The three maps of climate, population density and market access infrastructure were overlaid to create zones with homogeneous climate, demographic pressure and market access condition. This was done with the help of a geographical model, IDRISI (Eastmann 1988). Each climate/population density/market zone with < ha of cassava in each country was excluded as unrepresentative of cassava-growing areas. The remaining areas, which formed the potential survey regions, were divided into grids of cell 12 latitude by 12 longitude to form the sample frame for site selection. In each country, a certain number of grid cells, determined by the size of the country, were distributed among the climate/population density/market zones, in proportion to the sizes of the zones and were randomly selected. The total number of grid cells for the four sampled countries (Cote d Ivoire, Nigeria, Tanzania and Uganda) is 181 (figure 1). One village was selected, by a random method, within each of the grid cells. Table 1: Definitions of Climate and Altitude Zones Characteristics Zone Daily temperature ( 0 C) Dry season Mean Range (months) Lowland humid (LLH) >22 <10 <4 Highland humid (HLH) <22 <10 <4 Sub-humid (SH) >22 >10 6 Non-humid (NH) >22 > Low altitude (LA) <800 meters above sea level (masl) Mid altitude (MA) 800 meters above sea level (masl)

3 3 Asadu C. L.A, Nweke F.I. and Enete 3 A. A. Figure 1. Locations of the villages In each selected village, a list of farm households, was compiled and grouped into large, medium, and small smallholder units with the assistance of key informants. One farm unit was selected from each stratum (Nweke et al. 1994). Cassava yield data were then taken from fields 9-12 months old; this being the most frequent age of harvest in the areas surveyed. Soil samples were collected from all the fields (plots) of the three selected farmers from where cassava yields were taken at 0-20 cm and cm depth using a posthole auger. Two or more auger points were systematically selected depending on the homogeneity of the field to represent each field. Samples from each field were bulked separately before analysis. Where the field was sloping, it was divided according to slope position and samples from each topographic position bulked and analyzed separately. The altitude of each field was measured with an altimeter and all the fields were classified into either low (< 800 masl) or mid ( 800 masl) altitude fields All the laboratory analyses were done in the Analytical Service Laboratory of the International Institute of Tropical Agriculture (IITA), Ibadan following standard procedures outlined in the IITA (IITA 1982) Laboratory Manual. Soil properties determined include: particle-size distribution, organic matter, total N, available P, total S, exchangeable bases, exchangeable acidity, and total Mn, as well as soil ph (H 2 O). Various nutrient ratios were also calculated RESULTS AND DISCUSSION Fallow Systems Following Greenland (Greenland 1974), the COSCA study classified fallow periods into three: long fallow which denotes less than 10 years of continuous cultivation fallowed by 10 or more years of fallow; short fallow: referring to less than 10 years of continuous cultivation combined with less than 10 years of fallow between crops; and continuous cultivation involves at least 10 years of continuous cropping with less than one year of fallow between crops. About 20% of the village fallow systems were continuous cultivation, 75% short

4 Soil Properties and Intensification of Traditional Farming Systems in Sub Saharan Africa (SSA) 4 fallow and only 5% were long fallow systems. Intervillage variations in the fallow systems were due to demographic (Lagemann 1977) and market pressures (Nweke et al. 1994). Lagemann (1977) noted that farmers are able to change cultural practices and systems in response to increasing population pressure. For instance, about 30% of the high population village fallow systems were under continuous cultivation as against about 15% in the low population village fallow systems (table 2). Similarly, about 25% of the good marked access villages had continuous cultivation fallow systems compared to only about 10% in the poor market access areas (table 2). Organic Manuring Organic manuring was considered practiced if organic matter was brought in from outside to add to plant residues if any, already available in the field. Organic matter often brought into the field from outside included animal waste, household waste, etc composted or fresh, all with the aim of regenerating depleted soil nutrients Overall, the application of this intensive system in the study area was very low covering only 5% of the arable crop fields. The practice was more common in good than in poor market access areas, and in high than in low population density zones (table 3). The most important form of agricultural intensification is the substitution of manure for fallowing as the principal means of maintaining soil fertility (Ebo 1990). Livestock Grazing Livestock grazing was considered practiced if the field was grazed with sheep, goats or cattle prior to planting. The soil fertility value of livestock grazing is in the difference between the soil nutrients added by the droppings and that lost by the vegetation removed. For instance, it is expected that soils where animals graze under confinement will receive more animal droppings than those where they graze under free range. Livestock grazing was practiced in an average of about 15% of the arable crop fields surveyed. It was more common around market centers and in high population density zones than in areas remote from market centers and in low population density zones (table 3). Nweke et al. (1994) observed that while fallow periods declined as population density increased, the use of land use intensification practices such as livestock grazing became more frequent in an effort to counter the effect of reduced fallow on yield. Table 2: Percentage distribution of village fallow systems by population and market zone in SSA Zone Population density Market access high low good poor No. of systems Percentage Continuous cultivation Short fallow Long fallow Total Table 3: Percentage distribution of arable fields by soil fertility management practices by market and population zone in SSA Percentage Organic Manuring Livestock Grazing Zone N Practiced Not Total Practiced Not Total practiced practiced Market access: Good Poor Population: High Low N = Number of fields

5 Asadu C. L.A, Nweke F.I. and Enete 3 A. A. 5 Inorganic Fertilizers On the average, inorganic fertilizers were used in less than 10% of the fields, all in Nigeria. They were not reported used in any of the fields surveyed in Cote d Ivoire, Tanzania or Uganda. Compared to the last three countries, Nigeria had better market access conditions (Nweke et al. 1999). It is to be noted that inorganic fertilizer application is an intensive system which is more common in good than in poor market access areas. Land use intensification is always accompanied by fertilization practices to make up for the period of natural regeneration (fallow period) which range from ash fertilization to a combination of methods including artificial fertilization (Ebo 1990). Comparing Soil Properties Across Population and Market Pressures From this study, the applications of organic manure and other intensification practices generally increased as population density increase. This is reflected in the differences in the soil properties between high and low population density zones. The higher levels of available P, total N, and exchangeable Ca in the soils of the higher population density zone reflect the higher level of organic matter use in the zone (table 4). Lagemann (1977) observed greater use of household refuse and organic manure in high than in low population density villages in southern Nigeria. In addition, K +, EPP, C:N and Ca:Mg ratios were also higher in the soils of the higher population density zone. On the other hand, the higher levels of TEB and ECEC in the soils of the low population density zone which imply a higher overall nutrient reserve, (Asadu et al. 1998) may be a reflection of long fallow periods. In addition, ph, Mg ++, and Mg:K ratio were higher in low population density soils. The above suggest that the intensification practices at the high population density zones may not be sufficient to avert soil degradation. Nweke et al (1994) noted that the low frequencies of land use intensification practices in the high population density areas make it difficult to raise the level of cassava root yield in the area There were also significant differences between the good and poor market access zones in all the mean values of soil properties except available P and total N (table 5). The levels of exchangeable K, Mg, Na and ph and particularly of both TEB and ECEC were significantly higher in the soils of the poor than in the good market access zones. This also implies a higher nutrient reserve (Asadu et al. 1998) in the soils of the poor market access than those of the good market access zones. Fallow periods were significantly longer in the poor than in the good market access areas (Asadu and Nweke 1999). Thus, the better soil conditions in the poor market access areas could be because of the longer period of natural soil regeneration. In addition, farmers in the good market access areas are usually undercapitalized to use adequate and appropriate specification of purchased inputs that can counter the effect of short or no fallow on soils. (Enete and Achike 2008) Table 4: Mean values of soil properties by human population densities in SSA at soil depth of 0-40 cm Soil properties Low (N = 650) High (N = 1280) LSD (0.05) Avail P(mg/kg) Total N (%) OM (%) ph (H 2O) Ca ++ (cmol/kg) K + (cmol/kg) Mg ++ (cmol/kg) Na + (cmol/kg) TEB (cmol/kg) TEA (cmol/kg) ECEC (cmol/kg) BS (%) EPP (%) ESP (%) C:N ratio Mg:K ratio Ca:Mg ratio Notes: N = number of fields; OM = organic matter, TEB = total exchangeable bases, TEA = total exchangeable acidity, ECEC = effective cation exchangeable capacity, BS = base saturation, EPP = exchangeable potassium percentage, ESP = exchangeable sodium percentage.

6 Soil Properties and Intensification of Traditional Farming Systems in Sub Saharan Africa (SSA) 6 Table 5: Mean values of soil properties by zones of market access conditions in SSA at soil depth of 0-40 cm Soil properties Good access Poor access LSD (0.05) Avail P(mg/kg) Total N (%) OM (%) ph (H 2O) Ca ++ (cmol/kg) K + (cmol/kg) Mg ++ (cmol/kg) Na + (cmol/kg) TEB (cmol/kg) TEA (cmol/kg) ECEC (cmol/kg) BS (%) EPP (%) ESP (%) C:N ratio Mg:K ratio Ca:Mg ratio Notes: N = number of fields; OM = organic matter, TEB = total exchangeable bases, TEA = total exchangeable acidity, ECEC = effective cation exchangeable capacity, BS = base saturation, EPP = exchangeable potassium percentage, ESP = exchangeable sodium percentage CONCLUSIONS The use of all the soil maintenance strategies (organic manuring, livestock grazing and inorganic fertilizer) increased with population and market pressure. However, soils of the high population density and good market access areas were found to be generally poorer in nutrient than those of the low population density and poor market access areas. Thus the study shows that the intensification practices by farmers in SSA in the high population density and good market access areas are not adequate enough to counter the effect of short/no fallow. Fallow periods were generally longer in the low population density and poor market access areas. This observation underscores the need for credit availability to smallholder farmers to enable them apply the required specification of soil maintenance strategies which can counter the effect of reduced fallow periods on soils. REFERENCES Alia, A. (1984). Agricultural Stagnation Under Population Pressure: The Case of Bangladesh. VIKAS Publishing House PVT Ltd, New Delhi. Asadu, C.L.A. Nweke F.I., and Ekanayake, I.J. (1998). Factors affecting the fertility status of soils growing cassava in sub- Saharan Africa. Communications in soil science and plant analysis, 29 (1 and 2): Asadu, C.L.A and F.I. Nweke. (1999). Soils of Arable Crop Fields in Sub-Saharan Africa: Focus on Cassava Growing Areas. COSCA Working paper No. 18, COSCA, IITA, Ibadan, Nigeria. Asadu, C. L. A., F. I. Nweke and A.G.O. Dixon 2007). The contributions of Soil Properties to Cassava Yield Parameters in Sub-Saharan Africa Agro-Science, 6(1): Boserup, E. (1965). The conditions of agricultural growth, The Economics of Agrarian Change Under Population Pressure. G. Allen and Unwin Ltd, London. Carter S.E. and P.G. Jones. (1989). COSCA Site Selection Procedure. COSCA Working Paper No. 2, COSCA, IITA, Ibadan, Nigeria. Eastman, J.R. (1988). IDRISI. A Grid based Geographical Analysis. Mass Version 3.0. Worcester Clard University Graduate School of Geography. Ebo, E.C. (1990). Agricultural Intensification and Factor Productivity in Anambra State of Nigeria. A Case Study. PhD Thesis, Dept. of Agricultural Economics, University of Nigeria, Nsukka. Enete A.A and A.I. Achike (2008) Urban Agriculture and Urban Food Insecurity/Poverty in Nigeria: The case of Ohafia Southeast Nigeria. Outlook on Agriculture. (In Press) FAO. (2002). Reducing Poverty and Hunger the Critical role of Financing for Food, Agriculture and Rural Development. Paper Prepared for the International Conference on Financing for Development at Monterey, Mexico, March 2002, FAO, Rome, Italy. Fresco, L. (1986). Cassava in Shifting Cultivation: A Systems Approach to Agricultural Technology Development in Africa. Royal Tropical Institute, Amsterdam.

7 Asadu C. L.A, Nweke F.I. and Enete 3 A. A. 7 Greenland, D.J. (1974). Evolution and Development of Different types of Shifting Cultivation. Pages 5 15 in Report on the FAO/SIDA/ARCN Regional Seminar on Shifting Cultivation and Soil Conservation in Africa held at the University of Ibadan, 2 21 July FAO/SIDA/TF109, FAO, Rome, Italy. IITA. (1982). Automated and Semi-Automated Methods for Soil and Plant Analysis Manual Series No. 7, Ibadan, Nigeria. Jones, P. G (1988) Climate Version World Tropical Climate Database. Agroecological studies unit, CIAT, Cali, Columbia. Lagemann, J. (1977). Traditional African Farming Systems in Eastern Nigeria: an Analysis of Reactions to Increasing Population Pressure. IFO INSTITUTE FUR WIRTSCHAFTSFORSCHUNG MUNCHEN, Germany. Nweke F.I; A.G.O. Dixon, R. Asiedu and S.A Folayan. (1994). Cassava Varietal Needs of Farmers and the Potential for Production Growth in Africa. COSCA Working Paper No 10, COSCA, IITA, Ibadan, Nigeria. Ruthenberg, H Farming Systems in the Tropics. Clarendon Press, Oxford, UK. Nweke F.I, B.O, Ugwu, A.G.O. Dixon, C.L.A. Asadu and O. Ajobo. (1999). Cassava Production in Nigeria. A function of Farmer Access to Market and to Improved Production and Processing Techniques. COSCA Working Paper. No. 20, COSCA, IITA, Ibadan, Nigeria.